Checklist
Count rework as a forecast component
The second pass still consumes the calendar.
When it fits
- Plans assume work flows forward once, even when review and correction are normal.
When to avoid it
- Do not normalize chronic avoidable defects as inevitable rework; use the data to improve the process.
Checklist
- Review step included.
- Typical correction loop included.
- Revalidation included.
- Avoidable defect rework tagged separately.
- Unexpected rework captured for later learning.
Why it matters
For work with known review loops, estimate expected correction and revalidation effort explicitly rather than pretending first-pass acceptance is the default. Track why rework occurred so avoidable defects can be separated from normal iteration.
An example
A data migration estimate includes one validation-and-correction cycle instead of treating every failed row as an unforeseeable surprise.
Check your result
The plan includes the repeat work that normally occurs in comparable deliveries.
Keep this limit in mind
- Do not normalize chronic avoidable defects as inevitable rework; use the data to improve the process.
Connected ideas
Useful withExplain forecast error by component
Evidence and sources
The 2026 Green Book recommends explicitly accounting for optimism bias in cost, benefit and duration estimates and using historical forecast errors from similar proposals where available.
The guidance is for UK public appraisal; the transferable principle is empirical correction, not a universal percentage uplift.
The Green Book (2026) · Optimism bias
Supplementary Green Book optimism-bias guidance recommends basing adjustments on data from past or similar projects and collecting local data to improve future estimates.
Reference classes must be genuinely comparable; irrelevant historical projects can make an estimate worse.
Supplementary Green Book Guidance: Optimism Bias · Introduction and making adjustments